I. Field
This invention relates to wireless communication. More particularly, the invention relates to resource management, useful in an ad-hoc wireless communication system in which adjustments in signal power can provide an increase in spatial reuse of signal spectrum.
II. Background
In shared spectrum wireless communication systems, the capacity is in part determined by the signal power used to communicate with each user. This is affected by the total power transmitted by all transmitters within a particular geographical area, the relative power of each transmitter and the maximum power allocated to each device. In addition, the capacity is controlled by the data rate of each transmission.
Recent research has shown that multi-hop, radio frequency (RF) wireless networks are generally not scalable, and tire size and number of users is limited. When deploying a wireless local area network (WLAN), the aggregate signal throughput (the speed of sending information over time) of all users is what can be used to determine the number of users that an access point can support to provide adequate RF coverage.
For 802.11b networks operating at 11 Mbps, the total throughput capacity of an access point is about 6 Mbps. As a result, the access point in this example would support approximately 60 active users (6 Mbps/100 Kbps). If all users were viewing high quality streaming video, then the access point would only effectively handle about three users (6 Mbps/2 Mbps). In actual practice, it is very difficult to accurately determine the throughput requirements of individual users, and it is hard to predict utilization levels and traffic patterns. To obtain a clearer picture of throughput before deploying the network or making changes, it is possible to model 802.11 traffic in a network and view throughput levels under various conditions.
The data rate also controls the ability of a wireless communication to process signals at a given power in a given signal environment. Lower data rates permit decreased signal power for adequate reception and consequently permit the transmission to be made at reduced power while maintaining at least a predetermined minimum quality of service (QoS). By reducing the power while maintaining at least a predetermined minimum QoS, a local network is able to admit more users.